THS3061

THS3062

SLOS394A – JULY 2002 – OCTOBER 2002

www.ti.com

21

There are two simple ways to create an integrator with a CFB amplifier. The first, shown in Figure 56, adds a resistor

in series with the capacitor. This is acceptable because at high frequencies, the resistor is dominant and the feedback

impedance never drops below the resistor value. The second, shown in Figure 57, uses positive feedback to create

the integration. Caution is advised because oscillations can occur due to the positive feedback.

+

–

C1

Rf

Rg

VO

VI

THS306x

V

O

V

I

+

R

f

Rg

S

) 1

R

f

C1

S

Figure 56. Inverting CFB Integrator

+

–

Rf

VO

Rg

R2

R1

C1

RA

VI

THS306x

For Stable Operation:

R2

R1 || RA

≥

Rf

Rg

sR1C1

(

)

Rf

Rg

1 +

Figure 57. Noninverting CFB Integrator

The THS306x may also be employed as a very good video distribution amplifier. One characteristic of distribution

amplifiers is the fact that the differential phase (DP) and the differential gain (DG) are compromised as the number

of lines increases and the closed-loop gain increases. Be sure to use termination resistors throughout the distribution

system to minimize reflections and capacitive loading.

+

–

75

Ω

75

Ω

75

Ω

75

Ω

75

Ω

N Lines

VO1

VON

THS306x

75-

Ω Transmission Line

VI

Rf

Rg

Figure 58. Video Distribution Amplifier Application